Heat shield arrangement for a gas turbine combustion chamber

ABSTRACT

In order to cool the hot surface of the heat shield that surrounds the burner of a gas turbine annular combustion chamber as efficiently as possible, especially in the vicinity of the burner throughflow opening, a cooling air stream that escapes through a ridge that runs around the edge of the throughflow opening is guided by a guide rib in the direction of the throughflow opening. This guide rib is aligned essentially parallel to the ridge and on the combustion chamber side has an end that is bent in such fashion that the cooling air stream that flows into the gap between the ridge and the guide rib is deflected thereby in the direction of the hot surface of the heat shield.

BACKGROUND AND SUMMARY OF THE INVENTION

The invention relates to a heat shield arrangement for a gas turbinecombustion chamber with a heat shield having a central throughflowopening for a burner as well as a ridge extending circumferentially atthe edge of the throughflow opening. The ridge has a plurality of airblow-by openings for the cool air that is guided to the cold back sideof the heat shield facing away from the combustion chamber. Reference ismade regarding prior art for example to European Patent document EP 0471 437 A1 wherein, similarly to this known prior art, the present heatshield is also provided preferably for an annular combustion chamber.

The hot surface of the heat shield must be cooled intensively, for whichpurpose conventional heat shields have a plurality of cooling airthroughput openings through which the cooling air stream directed at thecold back side of the heat shield can pass through the heat shield andthus strike the hot surface of the heat shield, producing a film ofcooling air. However, it is not possible under these conditions tosufficiently cool the annular area around the burner throughflowopening, which is subjected to particularly high temperature stress. Inaddition, the cooling air stream that escapes in the vicinity of thethroughflow opening through the gap between a sealing part that receivesthe burner as well as the heat shield is insufficient for this purpose.

The goal of the invention therefore is to provide measures with whoseaid the cooling of the heat shield can be further improved, especiallyin the vicinity of the burner throughflow opening.

The solution to this problem is characterized by a guide rib providedinside the throughflow opening and aligned essentially parallel to theridge. The end of the guide rib on the combustion chamber side is bentat an angle in order to deflect the cooling air stream flowing inthrough the air blow-by openings into the gap between the ridge and theguide rib in the direction of the hot surface of the heat shield.Advantageous embodiments and improvements are described herein.

The invention is described in greater detail with reference to preferredembodiments.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic half section through a heat shield arrangementaccording to the invention;

FIG. 2 is a schematic half section through a heat shield arrangementaccording to the invention;

FIG. 3 is a schematic half section through a heat shield arrangementaccording to the invention;

FIG. 4 is a schematic half section through a heat shield arrangementaccording to the invention;

FIG. 5a is a schematic half-section of another embodiment according tothe invention; and

FIG. 5b is partial section view taken in the direction of arrow A inFIG. 5a.

DETAILED DESCRIPTION OF THE DRAWINGS

Referring to the figures, the cold back side of heat shield 1 is markedby reference number 2a, while the hot surface of the heat shield thatfaces the combustion chamber (not shown) has reference number 2b. Thisheat shield 1 as usual surrounds a burner, not shown, through which afuel-air flow is introduced into the combustion chamber of the gasturbine. For this purpose, the heat shield has a throughflow opening 3for the burner. Likewise in usual fashion, the burner is surrounded by asealing part 4. In addition, FIG. 1 shows a bolt 5 projecting from heatshield 1 behind throughflow opening 3. The bolt serves to fasten heatshield 1 to the combustion chamber head of the gas turbine.

Hot surface 2b of the heat shield must be cooled intensively. For thispurpose, a cooling air stream is guided to the cold back side 2a of heatshield 1. The cooling air stream (as shown in FIG. 1) penetrates atleast partially through a plurality of bores 6 in heat shield 1 and,since these bores 6 run at an angle to surface 2b, is applied as acooling air film to the hot surface 2b of heat shield 1. Similarly, aplurality of air blow-by openings 7 is provided in a ridge 8 provided onthe edge of throughflow opening 3, especially in the area of the backside 2a of the heat shield 1. Cooling air can then pass from back side2a to the area of throughflow opening 3 through these air blow-byopenings 7. In the embodiments shown in FIGS. 1 and 4, ridge 8 is partof heat shield 1 while in the other embodiments ridge 8 is part of aseparate annular element 11.

In order to cool intensively, in particular the marginal area of heatshield 1 in the vicinity of throughflow opening 3 using this cooling airthat passes through air blow-by openings 7 in ridge 8, a guide rib 9aligned essentially parallel to ridge 8 is provided. An end 9a of saidguide rib is bent on the combustion chamber side so that the cooling airstream, as indicated by arrow 10, is deflected in the direction of thehot surface 2b of heat shield 1. As a result, there is an annular gap 12between ridge 8 and guide rib 9, through which gap the cooling airstream passing through air blow-by openings 7 is guided and finallydeflected along the bent free end 9a of guide rib 9 in the direction ofthe hot surface 2b of heat shield 1. Preferably, free end 9a of guiderib 9 is aligned essentially parallel to beveled edge 1a of heat shield1 in the corner area of throughflow opening 3 and hot surface 2b (seeFIG. 1).

In the embodiment shown in FIG. 1, guide rib 9 is made in the form of aso-called annular element 11 located between a collar 4' of sealing part4 and ridge 8 provided on heat shield 1. This annular element 11 is bothsimple to manufacture and readily mounted on the likewise easilymanufactured heat shield 1.

In the embodiment according to FIG. 2, an annular element 11 is likewiseprovided between collar 4' and heat shield 1, said element 11 in thiscase forming ridge 8 and having air blow-by openings 7. Guide rib 9,which constitutes a separate, similarly annular component, abuts thisannular element 11. The air blow-by openings 7 in annular element 11 areprovided with vorticization devices so that the cooling air that passesthrough air blow-by openings 7 can be subjected to a desiredvorticization. A similar embodiment with air blow-by openings 7 withoutvorticization means is shown in FIG. 3.

In the embodiment according to FIG. 4, not only ridge 8 but also guiderib 9 are themselves parts of heat shield 1. Guide rib 9 is shaped onheat shield 1. In particular, heat shield 1 together with shaped guiderib 9 constitutes a cast part. In this embodiment according to FIG. 4,just as in the embodiments already described in connection with FIGS. 2and 3, the free end 9a of guide rib 9 extends into the combustionchamber of the gas turbine for a distance such that this free end 9aitself is directed parallel to hot surface 2b of heat shield 1. In thismanner, the cooling air stream that penetrates annular gap 12 is guidedespecially reliably and precisely against heat shield surface 2b.Otherwise, in this embodiment according to FIG. 4, the air blow-by holes7 are also provided with vorticization devices, represented by the crossgrid shown in the figure.

FIGS. 5a and 5b show another embodiment in which guide rib 9 is shapedon annular element 11 similarly to the embodiment in FIG. 1. In thisembodiment however the air blow-by openings 7 are in annular element 11,so that further measures are necessary to permit air to access these airblow-by openings 7. Therefore a ring 13, slotted in a gear-like manner,is provided between annular element 11 and collar 4' of sealing part 4,the toothed slots 13' of the ring 13 permitting air to access airblow-by openings 7. Not only in this embodiment but in the previous onesas well, a spacer 14 provided with air blow-by openings 14' is alsoshown, by which the sealing part 4 with its collar 4' abuts end wall 15'of the combustion chamber. The cooling air stream supplied passesthrough air blow-by openings 14' to the side of ridge 8 that faces awayfrom the combustion chamber, in other words the cooling air stream mustfirst pass through air blow-by openings 14' in order to then be able toflow through air blow-by openings 7 into annular gap 12 between ridge 8and guide rib 9 and then eventually be deflected by this guide rib 9 inthe direction of hot surface 2b of heat shield 1.

I claim:
 1. A gas turbine combustion chamber having a heat shield with acentral through-flow opening for a burner and a ridge running around anedge of the central through-flow opening, comprising:a plurality of airblow-by openings arranged in said ridge for cool air guided against acold back side of the heat shield which faces away from the combustionchamber; a guide rib located inside said through-flow opening andaligned essentially in parallel to said ridge, a combustion-chamber-sideend of said guide rib being bent at an angle in order to deflect thecool air entering through said plurality of air blow-by openings into agap formed between said ridge and said guide rib in a direction of a hotsurface of said heat shield; a sealing part collar arranged to surroundthe burner as well as the heat shield; wherein said guide rib has aposition between said sealing part collar and said heat shied.
 2. Thegas turbine combustion chamber according to claim 1, further comprisingan annular element arranged between said sealing part collar and saidheat shield, wherein said guide rib abuts said annular element.
 3. Thegas turbine combustion chamber according to claim 2, further comprisinga ring having a plurality of slots having a gear-like shape, said ringbeing located between the annular element and the sealing part collar,said plurality of slots permitting air to enter the plurality of airblow-by openings.
 4. The gas turbine combustion chamber according toclaim 1, wherein said plurality of air blow-by openings includevorticization devices.
 5. The gas turbine combustion chamber accordingto claim 2, wherein said plurality of air blow-by openings includevorticization devices.
 6. The gas turbine combustion chamber accordingto claim 3, wherein said plurality of air blow-by openings includevorticization devices.
 7. A gas turbine combustion chamber having a heatshield with a central through-flow opening for a burner and a ridgerunning around an edge of the central through-flow opening, comprising:aplurality of air blow-by openings arranged in said ridge for cool airguided against a cold back side of the heat shield which faces away fromthe combustion chamber; a guide rib located inside said through-flowopening and aligned essentially in parallel to said ridge, acombustion-chamber-side end of said guide rib being bent at an angle inorder to deflect the cool air entering through said plurality of airblow-by openings into a gap formed between said ridge and said guide ribin a direction of a hot surface of said heat shield; wherein said guiderib is formed on said heat shield.
 8. The gas turbine combustion chamberaccording to claim 7, wherein said heat shield and said guide rib are asingle cast part.
 9. The gas turbine combustion chamber according toclaim 7, wherein said plurality of air blow-by openings includevorticization devices.
 10. The gas turbine combustion chamber accordingto claim 8, wherein said plurality of air blow-by openings includevorticization devices.